2003 Volvo S60 AWD
 

Looking for some advice! I have a 2003 Volvo S60 AWD and my mechanic gave me the option of replacing the propeller shaft or removing it (turning the car into Front Wheel Drive). I opted to remove it as I am mostly driving around the city and the $1800 to replace it was a bit more than I was wanting to spend if not necessary.

I noticed the car loses control on hills when it is raining. Is this to be expected? Is removing the propeller shaft safe? Or should I get it replaced?

The way most AWD cars work is the wheel's speed sensors detect a speed difference between the front and rear wheels and that in turn engages the center differential lock to effectively transfer some of the power to the rear wheels. Since you removed the prop shaft, the rear wheels don't get that power transfer so you are effectively driving a front wheel car now - with perhaps a confused traction control system. So yes, front wheel slippage is to be expected. Note, removing the prop shaft is more common on the early XC70s when the bevel gear (aka transfer case) failed and the parts to repair were generally not available. You can keep driving as is with a lighter foot in bad weather or have the car repaired back to stock (which will help its resale value). I'd suggest the repair, particularly if its simply the shaft/bearings and if you are planning to keep the car for a while.